Thyroid UK
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Answer to the High T3 question?

Please see below an email reply to my question posed to a MD in USA. Rising TSH, low FT4 and high FT3.

Personally this doesn't help me as I'm still being told that as I'm creating enough of my own FT3 there is no need for T4 supplementation. However, this reply implies that low FT4 is low FT4 however you look at it. I know also that RT3 is not an issue so I should be ruddy wonderful!

How are we ever to get to the bottom of this when there is so much disagreement?


When is T4 supplementation needed?

Where TSH is steadily rising now at 2.8 and Free T4 is always low around 12 (range 10 - 24) but Free T3 is high 6.9 (range 0.5 - 5.7) would this still indicate the need to T4 supplementation? If conversion is doing so well what would be the point? This is in conjunction with SIBO, hair-loss, fatigue etc but with gluten,dairy and sugar free diet already in place. No antibodies, adrenals, vit d, ferritin and B12 all ok. Your thoughts would be most appreciated.


In this setting in my patients, the first question is are they taking any T3 containing products. If yes, then the test is meaningless and I would likely increase the thyroid dose if symptoms overall are suggestive in any case. If on no T3, I would check a reverse T3 level and if high, suggests that T3 is the preferred form of thyroid. If not, Armour thyroid.

11 Replies

so this doctor is telling you he/she would medicate you on NDT if no reverse T3 issues. What a 'good' doctor :)

my son had similar bloods last year, however fT3 was in top quarter of normal range and my private doctor wanted to treat, GP refused to acknowledge any problems existed.

fast forward to 7 months later he had TSH of 6.24 and fT4 of 14 and fT3 again top of normal range, GP now says there is something wrong and offered levo however my private doctor has put him on T3 as levo made him worse when he tried it.

He has started on 20mcg of T3 daily, and raised every week to 40, then stopped at 40 for 3 to 4 weeks, felt NO IMPROVEMENT all this time, so increased to 50 a week ago and ONLY YESTERDAY he told me he's BEGINNING to feel very slightly better now YAY :) we increased to 60mcg today :)

this doctor above you consulted is VERY clever and knows that bloods on T3 only mean 'nothing' :) could you PM me the details of who he/she is please? :)


Could you give me the details as well please



though this doctor is in America, so I will not go and see him/her from the UK, however, good to know for any friends/family who are over there :)


You will find him on

It was a long shot didn't think there would be a reply at all.

However, I still don't understand the mechanics of this. IF T3 is being produced in sufficient quantities by the body (liver, tissues etc) in the absence of a good supply of T4 with no RT3 issues then why the need to supplement at all?

Why is it considered necessary? Is this becuase the normal way of getting t3 is via deiodonisation of t4 and asking the body to produce it via tissues is not 'good' for us? Rather like buying something second-hand or poor condition?

Any takers with this please feel free to add your thoughts.


This is recent information to me but it has been mentioned twice and that is that the T3 is pooling in the blood for some reason. This makes the blood test show a high level of 3 but it is not being used. It may be somewhere in this webpage:

On the other hand, (for people adding T3)

Most of us need to spread the T3 out, not because it won't stay at a steady enough level in the system, but because it "uses up" Cortisol getting into the cells and if your body cannot produce Cortisol fast enough then temperature drops and you slump.



I have sent the results over to Dr M in Wales to see what she makes of it. I am interested in the cortisol connection as I do know that two years ago my cortisol was off the scale low so maybe its still about an adrenal problem more than anything else.

Apart from supporting the adrenals with all the natural ideas I can come up with the next stage would be cortisol itself but we all know that this is not normally treated on NHS unless its Addisons of course.

I'll post up somewhere what Dr M thinks of the results.




Please see my reply below. Can you shed any further light on this?


Hi It is considered that T3 must always be in range, but can be near the top, This is best near the top. It can be dangerous to the heart if over range, regardless of the other results, This is on the best info from my very best consultants, who are not obsessed by blood tests but by all the symptoms and how you feel being their best guide.If it was me ,I would have a little more T4 and some T3 providing you have had Free T3 tested and repeated after 6 weeks, All 3 tests. I have been on treatment a long time. there was no reverse test, although I certainly have Hashimoto, nothing known then, Hypo or Hyper only. However, on the correct treatment, for years my thyroid has been stable, first armour ,then when T3 came out armour and a little T3. It is considered better to be on T4 and T3 but I am allergic to Levo.I have normal below range FT3. I need it at the top of the range, but not over!It makes a huge difference to symptoms especially weight.Start on T3, script for 20 mcg , split ,12 hours apart. This is important as strong drug with side effects. Also for this reason good to start on half the dose split ( not easy) for the first week and only increase when sure there are no bad symptoms.

I hope that helps.


Not sure if you know , to reply to some one`s post, click on "Reply to this" under that post


Thanks Jackie

The thing is I'm not on any meds at all and never have been.

However, I have had terrible sympotms of Hypo and as my FT4 has been so low around 11-12 (range 9 - 24) for over 10 years and with my TSH risiing all the time 2.8 (range 0.4 - 6.0) I asked for a FT3 test to be done.

When this came back as high 6.9 (range 0.5 - 5.7) the GP whooped and said that this showed quite clearly that I am converting the little t4 I have perfectly well and am therefore NOT hypo at all.

I then arranged for a rt3 test privately which showed that this was low and not causing any probs. All of my other restuls, B12 ferritin etc have also been fine.

Then I contacted the chap above to see what he thought and he too suggested that supplements with t4 should be in place.

This is where I am now lost.

Some are saying that I would still need a good supply of t4, some are saying that the low t4 and high t3 (without any meds) shows that my body is struggling to create the t3 as compensation and this is not good, while others are saying that as long as my ft3 is top of range then I'm absolutely fine and the chap above says get Amour!.

This is all regardless of the awful symptoms over the years.

What I'm trying to establish is whether I should be pushing my GP to take this situation more seriously or not and if not what the hell is going on with all of my other symptoms (SIBO, fatigue, hairloss, eyebrow loss, swollen tongue etc etc etc).

Thanks for your thoughts.


Hi I see it certainly is complicated. One thing is that Hypo has sometimes identical symptoms to Hyper, I do not know much about Graves but I think this may be like that, and give variable results, auto immune. look at the Mayo clinic USA, the site the docs use ,very good and reliable.GP`s know little about thyroid ,very complex, you certainly should see a very good endo, research first as with everything, good and bad.The doctor in USA, may be just one with a "pet" theory a lot of those about. You do not want to have advice from any one unless absolutely sure of their credentials, ie a British endo, not a private thyroid doctor, not the same at all. A private endo also fine and they have more time than NHS but do also work in the NHS.Personally I think to take T4 with a high FT3 is risky without proper advice.However you do need to do something as it could affect the heart. I do not believe in all dire warnings about thyroid treatment but I see some of the best docs in the country and they are not "hung up "on blood results, High T3 is certainly not good..That is the course I would take and sooner rather than later. I would bot dream of speculating on how you should be treated, as I think it may be very dangerous.I would certainly ask for an ultra sound of the thyroid., too and I am sure a good endo will do lots of important test, not just the bloods.

best wishes,



Thanks for the reply Jackie. Really not sure why all this is the way it is.

I'm a little surprised that the TSH is still rising when the ft3 is also high as this would normally keep TSH down according to what I've read.

Anyway, will keep on with what I'm doing at present and see how I go.


Gilly x


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